Why does The Last of Us Part II stutter during stealth?

While sneaking through ruins, the screen would stutter every time more enemies appeared, which was incredibly jarring. I tried enabling Extreme Performance mode in the BIOS, but while max FPS rose, the 1% lows stayed at 40 FPS per RTSS. I then used the GamePP Resource Scheduler to bind the main process to high-performance cores and set the priority to Real-time. Frame times improved from 18-32ms to 11-15ms via GamePP Frame Analysis. GPU-Z showed temps at 62-74℃ and Cinebench R23 verified full multi-core performance.